If I read the situation correctly, the motorcycle with this screw is certainly not valueless. It can be turned into a working motorcycle far more easily than most other things can be turned into a working motorcycle. If it would take a competent technician an hour to remove the screw, then the screw shouldn't affect the selling price of the motorcycle by more than a couple of hundred dollars.
It's important to remember that small, trivial-seeming things can actually be important, which I think is what he's pointing at. But it's also important to remember that a thing's potential has value beyond its current abilities.
That is to say, without the screw, there is no motorcycle; without the motorcycle, there is no screw. In this concept, things cannot exist without being connected, dependent, and intertwined with one another. There is nothing that exists independently.
I won't defend the book vigorously, but your reading of this part seems both superficial and easily dismissed with a moments thought. Pirsig is obviously driving at something deeper, even if you don't think he completely gets there.
It's a book about thinking and changing how you do it, after all. You can't expect to get much out of something like that if you can't or won't examine your own cognitive bias as you do.
One of the major themes of the book is defining "quality" and "value".
Perhaps a bit with Chris, though, and maybe that is what you meant.
Back to the 'whole selling point' I think he was being overly dramatic, it's a novel after all. I think his point comes across better when he goes through the value traps part of the book, and interpret his point the following way:
Sometimes you are working on some machine (physical, like his motorcycle, or abstract, like software), and you get stuck on a problem due to a seemingly very meaningless part of said machine. I think his 'whole selling point' message is: when this happens, you need to reassess the value you give this part, as, until you get to resolve what it is causing it to get you stuck, its value to you is pretty much the value of the whole machine. Like how a crashing bug means that specific software is useless, in the specific use case that triggers the bug, until that is fixed. If it's some weird edge case, the software may be perfectly usable for most people, but if you are one of the few affected by it, the most likely few lines of code causing the defect render the whole thing useless, they're the selling point of the software to you individually.
Now, obviously, speaking of the actual physical motorcycle, it's not that he can't sell it without resolving the problem that particular screw is causing him. There are probably skilled mechanics with the right training and tools for which the screw would cause little to no problem. But to him: he can't ride it until that is resolved, so the screw is as important as the entire machine until he gets that resolved.
I faced this specific problem just a couple of days ago and remembering the book (which I read years ago) helped me step away from the problem and come back to it with a fresh angle. But the reality was the same: it's not that I would have lost my physical entity (a window, in this case). Surely, I could have called a professional carpenter to help me with it. But to me, without getting someone else involved, that little piece (it was also a screw, a rusty one) was worth the whole window.
If it can't fulfill this core function without the screw, it is valueless.
Of course, you can pawn the motorcycle for thousands of dollars, but for that, you would have to have a marketplace and buyers. You can also turn some parts into tools and probably repurpose the tyres into something useful.
But again, to do that, you would have to have the knowhow and the necessary tools and time for repurposing.
If you were in an isolated environment with no other people around and no additional tools, a motorcycle that doesn't function is as good as "valueless".
With that said, the motorcycle is clearly not value-less without the screw the same way it is not value-less without a rider.
The instant you dismount the motorcycle it is no longer physically capable of performing its function. Yet it of course still has value.
I don't think your comparison makes sense. A motorcycle is not broken without a rider; it is not being used to move from point A to point B, but it is capable of being used to move from point A to point B.
A broken motorcycle is not being used to move from point A to point B, however it is not capable of being used for that purpose. The broken motorcycle is clearly at a lower state than a functional motorcycle.
Perhaps a comparison that works would be (a broken motorcycle + a rider) is as worthless as (a working motorcycle + a broken/ignorant rider).
Neither can be used to move from point A to point B without the addition of their missing component.
If we assume I have the appropriate skills/training to successfully operate the motorcycle that is missing a rider can we not just as easily assume that I have the appropriate knowledge/materials to add the missing screw?
E: The point I'm trying to make is that it is the same scenario. We could argue over which assumption is more practical (how hard is to to find and install the screw vs ride a motorcycle) but that is a separate point.
The screw seems most important when it is the 'weak link'.
But the same is still true of all other components.
I guess Pirsig was making a point about value and not about potential value, which is leading to a larger point. In the moment, value is all you have. Potential value is a future value that requires time to realize.
I have two separate reactions to your suggestion that it's important to remember potential value, the Zen reaction and the Writer's reaction.
Even though Pirsig wasn't going for Buddhism, it's fairly consistent with Zen thinking to make observations about the momentary values of things. My Zen point is that the purpose of meditation and much of Buddhist practice is to see only value and to eliminate potential. When you learn about how to meditate, you learn how to stop your mind from thinking about the future and concentrate completely on the here and now. Remembering something's potential value is antithetical to this way of thinking. Not because it's untrue, but because it's un-now.
My writer's reaction is that while it will always be important to remember things other than the point the author was making. Is adding your point to the author's words helping us to understand his? If Pirsig reminded us about potential value in this sentence, would it improve this particular narrative? Does it open a path that gets to his larger point either more efficiently or more effectively? It might, that might be part of Pirsig's thesis. Or it might be taking a narrative path that doesn't lead to the same place.
It's important to see not just the value of the quote itself - the truth or completeness of an individual passage - but to also remember the potential value of the words as being the destination of the story -- where they lead and where it ends is as important as where it was at any given moment.